Перефразируйте следующие предложения,используя конструкцию complex object. 1. I believe they are

1. I believe they are very good at physics and other pure sciences. I believe them to be very good at physics and other pure sciences.
2. When he opened the window he heard how the birds were singing in the garden. When he opened the window he heard the birds singing in the garden.
3. I heard that his name was mentioned several times during the conversation. I heard his name mentioned several times during the conversation.
4. I saw that he opened the door and left the room. I saw him open the door and leave the room.